Street cleaning vehicles generally include refuse collection systems which transfer sweepings into a vehicle mounted refuse hopper. The sweepings are typically transferred into the hopper via a large conduit which has at least a partial vacuum provided by a vehicle mounted suction pump. Many systems include a water spray applied to the street proximate the sweeper brushes during the street sweeping operation, so that water and damp debris are sucked through the conduit and deposited into the vehicle debris hopper. Other systems employ mechanical brushes which sweep debris onto a conveyor belt for transfer to the debris hopper.
The debris hoppers for such vehicles generally include some means for transferring their contents to a separate stationary receptacle after they fill with water and debris. The hoppers are generally emptied by tilting, or some combination of lifting and tilting, to dump their contents into the stationary receptacle. Such a tilting, or combined lifting and tilting, operation has resulted in excessive spillage of the hopper contents because a hopper so tilted, or both lifted and tilted, has insufficient lateral displacement to prevent some spillage of discharge from hopper to receptacle. This inevitable spillage causes costly cleanup procedures during the dumping operations.
The FMC Vanguard 3000 sweeper vehicle is a typical example of a simple tilting hopper discharge arrangement. The hopper rotates around a fixed offset pivot point to tilt its rearward side lip over a stationary refuse receptacle. The tilting action is controlled with extendable cylinders mounted between the hopper and the sweeper vehicle support platform, with each cylinder on an opposite side of the hopper transverse to the pivoted side of the hopper. A lip discharge baffle plate, rotatably mounted below the rearward discharge lip of the hopper, serves to reduce discharge spillage. The fixed offset pivot point about which the hopper rotates also serves to minimize spillage. However, the baffling and fixed offset pivot point still do not eliminate spillage to a satisfactory degree. Furthermore, the height of the fixed offset pivot point for the hopper must be in the range of the height of the refuse receptacle into which the hopper discharges so that the lip of the hopper can clear the lip of the receptacle. Consequently, the hopper must rest on the vehicle platform at a higher level than might otherwise be desirable, thereby adversely affecting vehicle stability.
The Elgin Pelican and the Athey Mobil II are examples of sweeper vehicles which rely on a combination of lifting and tilting the hopper for the hopper discharge operation. Each side of the hopper is rotatably connected to the vehicle platform with a support bar. The support bars swing the hopper upward to bring the hopper to the desired height for discharge into a debris receptacle. The tilting operation of the hopper to discharge its contents is secured by adding two serially connected bars between the hopper and each of the support bars. The combination forms a four-bar linkage on each side of the hopper, with the hopper serving as a first bar, the support bar as a second, and the serially connected bars as third and fourth bars, respectively. One of the serially connected bars on each side of the hopper is connected to a cylinder which rotates the linkage to which it connects as the cylinder is extended, thereby forcing the hopper to rotate about the support bars to which it connects, allowing the hopper to discharge into the receptacle.
Although this system allows for operation of the sweeper vehicle with its hopper close to street level for maximum stability, even when the debris receptacle into which it must dump its contents has a significant height, the hopper must be lifted into position for discharge as described above. Furthermore, because of the necessity for swinging the hopper up to the desired height for discharge, the vehicle must move the hopper over the debris receptacle only after the hopper is swung up to the desired height. This is because of the necessity for providing sufficient clearance for the hopper from the debris receptacle to permit the hopper to swing. The necessary clearance so provided then prevents the hopper from discharging into the receptacle when so positioned. Moving the vehicle when the hopper is lifted to better position it over the receptacle is an undesirable step because inefficiencies of use and possible instabilities created by the height of the hopper when raised. Outrigger supports are not usable in this instance to improve stability because of the necessity for moving the vehicle to best position the hopper.
The RAVO Models 200 and 250 are sweeper vehicles which raise the whole hopper while tipping its rearward side toward a debris receptacle for discharge. This is accomplished with a crossed four-bar linkage lift arrangement along each of opposite sides of the hopper, with the hopper and vehicle platform each serving as respective first and second bars, a rigid support bar between the platform and hopper as a third bar, and an extendable cylinder, between the platform and hopper, and mounted crosswise to the rigid support bar, serving as the fourth bar. The crosswise configuration of the linkage system causes the hopper to tilt toward a debris receptacle as the hopper is raised by extending the cylinders. However, the tilting action so provided is insufficient to permit dumping the hopper contents from the lip of the hopper. Instead, a trap door on the rear of the hopper adjacent the debris receptacle is released after the hopper is tipped to provide a discharge path for the hopper. The trap door discharge system is prone to sealing and spillage problems.
The RAVO Model 4000 Container Dump style sweeper vehicle simultaneously lifts and rearwardly displaces its hopper to position the hopper discharge door over a high-walled debris receptacle. The hopper is lifted by two substantially parallel cylinders along each side of the hopper between the hopper and the vehicle platform. The hopper is guided rearward towards the debris receptacle by two four-bar linkages arranged on each side of the hopper between the bottom of the hopper and the vehicle platform. The hopper and the vehicle platform serve as respective first and second bars, and the two rigid support bars connecting them on each side as the third and fourth bars. As the cylinders lift the hopper from the vehicle, the twin four-bar linkages force the hopper rearward to position its anterior discharge door over the debris receptacle. This model does not have positive tilting action to insure complete discharge of the hopper contents into the debris receptacle.